The invention is directed to a process for the production of 3-methyl pyridine by catalytic reaction of acrolein and propionaldehyde with ammonia in the gas phase.
It is known that in the reaction of acrolein with ammonia in the gas phase in the presence of catalysts 3-methyl pyridine is formed. As catalysts there have been especially used compounds of the elements Al, F and O which additionally contain at least one element of the second, third or fourth groups of the periodic system and which have been treated with oxygen at temperatures of 550.degree. to 1200.degree. C. (German Offenlegungsschrift No. 2,151,417 or corresponding Beschke U.S. Pat. No. 3,898,177) or at least two elements of the second, fourth, fifth or sixth groups of the periodic system (German OS No. 2,224,160 or corresponding Beschke U.S. Pat. No. 3,960,766), or at least one element of the second main group of the periodic system (German OS No. 2,239,801 or corresponding Beschke U.S. Pat. No. 3,917,542. It is also known to carry out the reaction in a fluidized bed with the acrolein fed in separately from the ammonia (German OS No. 2,449,340 and corresponding Beschke U.S. Pat. application No. 622,488 filed Oct. 15, 1975). The disadvantage of these processes is that besides 3-methyl pyridine there is also formed to a considerable extent pyridine and the yield of 3-methyl pyridine is below 50%.
Furthermore, it is known to produce 3-methyl pyridine by reacting a mixture of acrolein and propionaldehyde with ammonia. As catalysts there are used aluminum oxide, silica or silica in admixture with 5 to 50% of aluminum oxide, in a given case with the addition of oxides of additional elements (French Pat. No. 1,273,826). In this process the yield of 3-methyl pyridine in the best case is 53% (Example 29).